On Mar 28, 2011 7:32 AM, "Stefan Sperling" <s...@elego.de> wrote: > > On Sat, Mar 26, 2011 at 09:46:48AM -0400, Greg Stein wrote: > > If it only needs to detect a single row, then LIMIT 1 should be in the > > query. > > Is there really a significant difference between LIMIT 1 and not stepping > through more than one result row? > > I'd rather keep the queries reusable for contexts where a complete > list of modified nodes is required, instead of adding COUNT() (as > suggested elsewhere) or LIMIT 1.
Think about how the query optimizer/planner would work. Consider whether a result set needs to be constructed. ... a LIMIT 1 provides a ton of help to the SQL engine about what needs to be fetched (or not). There is also a semantic element to it. Readers of the code will see that you're looking for basic presence rather than a set of results. If/when you need a query containing the set of nodes with mods, then you can consider another query. Until that time, the LIMIT is helpful/best. Cheers, -g
